The invention relates to apparatus for detecting the wear of motor brushes for signaling the need to replace the brushes before damage occurs to the armature, and more particularly relates to a method of indicating brush wear in a DC motor which utilizes a plastic commutator end head.
In appliances such as motors or generators having a rotating armature, a plurality of brushes make sliding electrical contact with the armature as it rotates. The brushes are typically made of a carbon particulate such as graphite and a binder material and may also include metallic particles. One or more holes are drilled in the end of the brush to accommodate current carrying wires which supply current to the brushes. In order to avoid damage to the armature contact surface after the brushes have worn down, a signal is generated when the brush wears to a predetermined point. Generally, a method of brush wear detection involves imbedding an insulated wire into a brush. As the brush wears, eventually the insulation on the wire will be worn away by the rotating commutator. An electrical circuit is completed when the wire touches the commutator.
In order to embed the wire within the brush labor is required as well as cost in the embedding procedure. It would be highly desirable to define a low cost method for indicating brush wear.